I would def go for a fresh look, the apple theme has been beaten to death.

First thing to do, like you mentioned, is come up with some art. Just start with a home screen and work from there. Begin with a black and white wire-frame layout, then add colors and effects. See where it takes you. Also consider that skins at minimum have an "on" state and an "off" state, so the skin has life when you hit buttons. Each state uses a separate graphic file.

Trying to make a skin to please the masses is not a good way to start as a beginner, focus more on what YOU want the skin to do and look like and it will make your learning curve much easier.

Throw an idea or two out there, we all critique each others work and are more than willing to lend a helping hand with the code.